Stripping device

ABSTRACT

In the case of a stripping device ( 3 ) for use with a cutting tool ( 1 ) with a cutting element, in particular a punch ( 2 ), for machining a workpiece, in particular a curved metal sheet ( 6 ), at least one fastening piece ( 4, 28, 40 ) for fastening it to the cutting tool, a spring-elastic element ( 21 ) arranged outside the workpiece contact region, a stripping element ( 15, 34 ) which comes into contact with the workpiece and surrounds the cutting element ( 2 ), and at least one guide element ( 11, 26, 33 ) guiding the stripping element ( 15, 34 ) being provided, a device for securing against rotation is provided to essentially prevent the stripping element ( 15 ) from rotating.

BACKGROUND

1. Field

The invention relates to a stripping device for use with a cutting toolwith a cutting element, in particular a punch, for machining aworkpiece, in particular a curved metal sheet, at least one fasteningelement for fastening it to the cutting tool, a spring-elastic elementarranged outside the workpiece contact region, a stripping element whichcomes into contact with the workpiece and surrounds the cutting element,and at least one guide element guiding the stripping element beingprovided.

2. Description of the Related Art

Stripping devices are known in conjunction with various types of cuttingtools (DE 196 05 113 A1, DE 40 35 938 A1, DE 42 35 972 A1 and WO99/67038 A1). A stripping device of this type is required for enabling,in particular in the case of punches or other cutting elements, themachined workpiece, in particular metal sheet, to be stripped off fromthe cutting element, in particular punch. During the cutting process, inparticular punching process, a front surface of the stripper is placedagainst the surface of the workpiece, deflects inward somewhat duringthe penetration of the workpiece by the punch and, when the cutting toolis pulled back out of the workpiece, springs out again, thus ensuringthat the, for example, punch will be pulled out of the workpiece.

Various models of strippers are available commercially. Most of themhave a fastening plate by means of which they can be fastened to thecutting tool, in particular a punch fastening plate. The stripper bodyis composed, for example, as a rubber spring of a hard plastic, thefront surface of which is formed in accordance with the contour of theworkpiece. The shaping can be undertaken here by trimming. The rubberspring surrounds the punch on all sides. In most cases, the shape of thefront surface of the stripper is not symmetrical, since the workpiece tobe machined generally has an irregular shaping.

U.S. Pat. No. 2,168,377 discloses a stripping device for use with apunch for machining a flat, planar metal sheet, in which an outerelement is fastened to a specially configured retaining plate of acutting tool via screws and bolts. The outer element is provided on itsinside with a longitudinal opening into which a stripping element, andin it the punch, are fitted. A spring-elastic element in the form of ahelical spring is fitted between the stripping element, the outerelement and the punch. The stripping element has an essentially straightsection and a protruding section, which can be supported on a projectionwithin the longitudinal opening of the outer element or is securedthereon in order not to be pushed inadvertently out of the element.

U.S. Pat. No. 1,723,935 discloses a similar construction of a strippingdevice as the above publication. In the same manner as said publication,U.S. Pat. No. 1,723,935 also uses a helical spring which is arrangedwithin an outer guide sleeve between punch, stripping element and aspecial fastening device for fastening it to the cutting tool. The outerguide sleeve is screwed onto a fastening piece which is fastened to afurther fastening piece which is connected via a flange to the cuttingtool via a screw connection.

U.S. Pat. No. 4,993,295 discloses a stripping device for use with apunch for machining a planar metal sheet, in which, as in U.S. Pat. No.1,723,935, guide surfaces between an outer guide sleeve and a strippingelement are relatively short, which means that, in the event of higherloads, the stripping element may tilt within the guide sleeve. Asspring-elastic element, various disk springs are provided which arelayered on one another within the guide sleeve in such a manner that thecurved surfaces in each case are directed toward one another. A punch isarranged within the spring-elastic element.

The stripper also has the task of keeping the workpiece in the desiredshape during the machining process. This is particularly important ifpunchings are to be undertaken in the region of metal-sheet edges, sincedeformations may easily occur there because of the punching process.However, the stripper is not intended to automatically deform theworkpiece, but merely to keep the latter in the desired, premanufacturedshape. If a rubber spring stripper which completely surrounds a punchand has an irregular front shaping facing the metal sheet is provided,this proves problematic if the stripper, after a number of punchingprocesses, rotates around the punch. The shaping of the surface of thestripper then does not correspond to the shaping of the surface of themetal sheet which is to be punched, for which reason problems of qualityand complaints may occur in this case.

For this purpose, DE 812 498 discloses a stripping device for a punchwith a helical spring which is arranged between a stripper plate and apunch head. The helical spring surrounds the region of the punch. Threestrips are provided which are fastened between the punch head andstripper plate and maintain a distance between these two elements. Thefastening takes place via screws and elongated holes, so that thedistance between stripper plate and punch head can be adjusted. Bycontrast, a rotation of the stripper plate is scarcely possible becauseof the strips.

FR 1 456 310 discloses a stripping device which, in one embodiment,comprises a helical spring and, in another, comprises an elastic elementwhich is fitted between two fixed plates. In the case of the secondembodiment, a screw bolt is arranged between the two fixed plates, in asimilar manner as provided by the strips in DE 812 498 for stablyconnecting the two plates. The screw bolt can also prevent the platesfrom rotating in relation to each other.

However, these publications do not disclose any possibility of allowingmatching to the particular shaping of deformed metal sheets. In all ofthe publications only straight metal sheets are ever punched. However,it is required in particular in the automobile industry to providestripping devices which match the particular shapings of deformed metalsheets or can be matched to them without any problem, essentially do notleave any traces on the punched metal sheets and have a long servicelife, i.e. of such stable design that they withstand a large number ofstrokes, in particular more than one million strokes without anymaintenance. In addition, the stripping device is to be designed in sucha manner that a simple and rapid changing and interchanging of strippingdevices can be undertaken. This is not possible with the devices of theprior art that are fastened to the cutting tool in a complicated manner.

In order to prevent rotation, Dayton Progress GmbH has also disclosed aspring-mounted steel stripper. A means of securing against rotation forthe punch is formed by the punch being constricted in cross section in asubregion and being flattened in rectangular form. A section of thestripper, which section is fastened to the steel stripper by means ofscrews, engages in this region.

This solution proves to be disadvantageous because of its susceptibilityto failure due to limited stability in the region of the small fasteningscrews and risk of fracture of the constricted punch. Since theindividual parts of a stripper have to be matched precisely to oneanother and a complicated mounting is frequently required, in the caseof alternatives manufactured manually average prices of 1800 euros perpiece arise. In contrast to this, the pure rubber strippers, asdescribed further above, cost approx. 100 euros per piece. However,these have the disadvantage, in addition to the disadvantages alreadymentioned above, that, when a metal sheet is punched from the inside,only small piece numbers for use with only certain shapes are possible.The steel stripper also has the disadvantage that the screws retainingthe engaging section on the steel stripper are very small and frequentlydo not permanently withstand the forces which occur, particularly sincesaid screws are loaded transversely. The durability of a rubberstripper, as described above, is approx. 80 000 strokes, meaning thatcorrect stripping is no longer ensured or possible and the manufacturingreliability is therefore impaired.

SUMMARY

The present invention is therefore based on the object of providing animproved stripping device which is stable and in which, in particular, asecuring against rotation within the range of a hundredth of amillimeter is possible and unilateral shearing forces can be eliminated.In addition, high numbers of strokes of, in particular, more than onemillion strokes are to be possible in particular for use in theautomobile industry, i.e. the durability and stability are to beimproved in comparison to the stripping devices of the prior art. Inaddition, the stripping device is to be comparatively cost-effective andas compact as possible.

This object is achieved by a stripping device with a device for securingagainst rotation being provided to essentially prevent the strippingelement from rotating.

A stripping device for use with a cutting tool with a cutting element,in particular a punch, is thus provided, in which a long-term durabilityof the spring-elastic element is made possible, since the latter doesnot come into contact with the workpiece. In addition, it is preferablyloaded centrically and in a manner free from torque, as a result ofwhich a nonuniform wear or loading is likewise prevented. A durabilityof the spring-elastic element of more than one million strokes is thuspossible. Owing to the use of a number (visible at a glance) ofindividual parts which, plugged together, produce the stripping device,the latter is more robust than the stripping devices of the prior art.The use of a guide element, preferably of guide sleeves or guidebushings, advantageously also enables a reproducible movement of thestripping device in relation to the cutting tool or the cutting element,in particular a punch. In addition, guidance by means of columns is nolonger necessary, as is required in numerous strippers of the prior art,in order to enable it to be attached fixedly in the cutting tool. Suchcolumns are intended, in particular, to intercept transverse forceswhich may occur during the cutting process and may rotate or displacethe stripper. In addition, a more cost-effective solution is providedthan, for example, in the case of the usual, manually constructed steelstrippers of the prior art. This is made possible, in particular, by thefact that the manufacturing outlay is very much smaller than in theseproducts.

The arrangement of the spring-elastic element outside the workpiececontact region affords various advantages. By this means, thespring-elastic element is no longer constantly in contact with oils andgreases which gradually corrode and destroy it. In addition, by means ofthe contact of the workpiece with the stripping element instead of thespring-elastic element, an essentially inflexible contact surface isprovided which enables the workpiece to be kept in shape and,conversely, is not deformed by the workpiece. The stripping elementtherefore particularly preferably consists of bronze or of anothermaterial which can be matched to the shape of the workpiece surface andis firm enough not to be able to be deformed by the workpiece during themachining process. A material is preferably selected which makes itpossible to configure the stripping element individually in respect ofits front surface shape in order to match the latter to the workpiece tobe cut. The spring-elastic element is preferably a rubber spring orpreferably consists of another spring-elastic, restoring and/or flexiblematerial. Particularly when a rubber spring is used, a fatigue fracture,for example of a helical spring, can be avoided.

The device for securing against rotation preferably comprises astripping element with an irregular cross-sectional shape and/or anelongated hole or polygonal hole in the guide element. It has provenparticularly advantageous if the device for securing against rotationhas a pairing, formed asymmetrically at least in one orientation, ofstripping element and hole or opening in the guide element so as toensure that the stripping element will be installed with a uniqueorientation, in particular an elongated hole with three straight sidesand one curved side and a correspondingly designed stripping element.The provision of a stripping element with a nonuniform cross section orasymmetrical shape at least in part and, in particular, of a crosssection, matched thereto, of the opening in the guide element in whichthe stripping element is guided, a rotation and a wrongly orientedinstallation of the stripping element in the guide element can beessentially avoided. By virtue of the provision of an elongated hole orpolygonal hole and/or of a stripping element with an irregularcross-sectional shape, an unambiguous position is specified for theinstallation, so that the stripping element, which is shaped on itsfront surface in accordance with the contour of the workpiece, cannotinadvertently be installed rotated in its position even when changedrapidly. In addition, a more rapid installation is possible, since theprecise position of the stripping element does not first have to bedetermined, but rather is predetermined by the shaping of the strippingelement and of the opening in the guide element, preferably of the guidesleeve or guide bushing, and by the preferred provision of inner andouter guide surfaces on the stripping element. A more rapid, easier andmore precise installation of the stripping device on the cutting tool istherefore possible than is possible in the case of the stripping devicesof the prior art. In addition to the rapid and easy installation andchanging of a stripping element and the correct orientation, this alsoenables damage of the workpiece which is to be punched to be avoided.Even metal sheets of complex shape can therefore be machined essentiallywithout damage, in particular likewise because of the advantageouspossibility of matching the front surface of the stripping element tothe shape of the workpiece, in particular metal sheet, as a result ofwhich markings of the workpiece around the punched hole can be avoided.In the case of the stripping devices of the prior art, such markingsregularly cannot be avoided, since the front surface shape of thestripping element is not matched to the shaping of the workpiece (shapedmetal sheet) which is to be machined (punched). For example, in the caseof vehicle doors, after the three-dimensional shaping thereof, holeshave to be provided in the lower region, the punching of which holesusing the above-described devices of the prior art is not possiblewithout damaging the door profile, since in this case neither a securingagainst rotation nor a matching of the shaping of the front surfaceregion of the stripping element to that of the door profile areprovided.

The spring-elastic element is preferably arranged between strippingelement or guide element and cutting tool and/or within the guideelement. This avoids contact of the spring-elastic element with theworkpiece. In addition, the spring-elastic element is held fixedly inthe stripping device. By this means, a uniform loading is possible whichkeeps the wear of the spring-elastic element as small as possible. Inaddition, a defined position of the spring-elastic element isestablished, an interchanging of said element in the case of wear alsoeasily being possible at any time.

The stripping element and the spring-elastic element are preferablyoriented, surrounding the cutting element, in such a manner that theycan be loaded in a manner essentially free from torque and, inparticular, centrically. This advantageously avoids a nonuniform wearand a tilting of the spring-elastic element and of the strippingelement. In addition, a reproducible position of the spring-elasticelement is predetermined, in particular for the interchanging situation,which means that an interchanging can be carried out rapidly and withoutany problem.

At least one guide sleeve is preferably arranged as a guide elementoutside the stripping element, at least partially surrounding the latterin a guiding manner, and/or at least one guide bushing is arranged as aguide element within the stripping element, guiding the latter. Theprovision of a guide element enables the stripping element to be guided,which permits a defined movement of the stripping element along thecutting element, in particular punch. In addition, the stripping elementpreferably has at least one guide surface on its inside facing a fittedcutting element, in particular the stem thereof. This permits thestripping element to also be guided along the cutting element, inparticular the stem thereof. An inner and outer guidance of thestripping element is therefore possible. A tilting as occurs inparticular in the case of rubber springs of the prior art no longer hasto be of concern. On the contrary, the exact movement is stillmaintained even after more than 1 000 000 strokes.

The stripping element preferably has an essentially straight section anda protruding section, guide surfaces being provided on the straight andthe protruding sections of the stripping element. At least one guidesurface is preferably provided between stripping element and guideelement, the length of which surface can be selected as a function ofthe forces acting on the stripping device, in particular shearing andlateral forces, in order to ensure tilt-free guidance. The provision ofa straight and of a protruding section of the stripping element providesan even better means of securing against tilting in relation to thecutting element and the guide element, since two guide surfaces areprovided which are arranged, in particular, at a distance from eachother. The particular length of the guide surface or guide surfaces canbe selected as a function of the forces acting on the stripping device.In this case, a longer guide surface is preferably selected if theforces which occur are higher.

In order to improve the sliding of the stripping element within theguide element, a lubricant, in particular a lubricant suitable formaintenance-free lubrication, in particular a solid lubricant, ispreferably provided at least in a subregion of the straight section. Theuse of a solid lubricant proves advantageous particularly in thematerial pairing of bronze and hardened steel for the individualelements sliding on one another. In particular, a combination of oil andgraphite is suitable as the solid lubricant. The provision in particularof maintenance-free lubrication is not provided in the prior art, forexample U.S. Pat. No. 2,168,377, U.S. Pat. No. 1,723,935 and U.S. Pat.No. 4,993,295. In these cases, a lubrication of the surfaces sliding oneinside another can be brought about only by disassembling the entiredevice. However, maintenance-free lubrication proves advantageous onaccount of the poor accessibility of the lubricating points and theotherwise long service life of the stripping device.

The guide element is preferably formed integrally with the fasteningpiece or guide element and fastening piece are formed as elements whichcan be joined together. An integral formation is suitable in particularin the case of higher forces, since, in this case, an inadvertenttilting of guide element and fastening piece one inside the other doesnot have to be of concern. The stability and compactness of thestripping device are therefore increased. By contrast, the formation ofguide element and fastening piece as elements which can be joinedtogether is suitable, in particular in the case of lower forces. Thisadvantageously, in particular, also enables just one fastening with justone fastening means, in particular a screw, to be selected. As a result,the fastening piece can be designed such that it is smaller and thusmore space-saving.

At least one protruding region and/or protruding section, in particulara claw- or clamp-shaped section, is or are particularly preferablyprovided on the circumference or edge of the fastening piece forengaging around a fastening device of the cutting tool. This enables thefastening piece to be centered on the fastening device, in particular afastening plate. A secure and centered fastening or locking of thestripping device to the cutting tool or the fastening device thereof is,as a result, also possible by means of just one single fastening means,in particular a screw. A compatibility of the fastening piece with astandardized fastening plate of a cutting tool proves very advantageous,since, as a result, a manufacturing of individual parts, as in the caseof the stripping devices of the above-described prior art, does not needto take place and an accuracy in terms of location is provided on eachexisting fastening plate. A rapid and easy interchanging of a strippingdevice is therefore possible even for unskilled operating personnel.

The stripping device is particularly preferably used together with aV-belt drive, since, with a drive of this type, not only canparticularly high forces be transmitted, but this also has to take placeparticularly accurately. In this case, the means of securing againstrotation lies within the range of a hundredth of a millimeter, whichcannot be obtained with the stripping devices of the prior art.

BRIEF DESCRIPTION OF THE DRAWINGS

To further explain the invention, a number of exemplary embodiments aredescribed in more detail below with reference to the drawings, in which:

FIG. 1 shows a schematic diagram of a punch installed in a cutting tooltogether with a stripping device according to the invention during theprocess of punching a metal sheet,

FIG. 2 shows a sectional view of a first embodiment of a strippingdevice according to the invention,

FIG. 3 shows a sectional view, rotated through 90°, through thestripping device according to FIG. 2,

FIG. 4 shows a plan view of the stripping device according to FIG. 2,

FIG. 5 shows a longitudinal sectional view of a second embodiment of astripping device according to the invention for use in the case ofaverage forces which occur,

FIG. 6 shows a plan view of the embodiment according to FIG. 5,

FIG. 7 shows a longitudinal sectional view, rotated through 90°, of thestripping device according to FIG. 5,

FIG. 8 shows a plan view of a further embodiment of a stripping deviceaccording to the invention with a stripping element which is rotatedthrough 90° with respect to the embodiment in FIG. 6,

FIG. 9 shows a longitudinal sectional view of a further embodiment of astripping device according to the invention for severe forces whichoccur,

FIG. 10 shows a longitudinal sectional view of the stripping deviceaccording to FIG. 9, and

FIG. 11 shows a plan view of the stripping device according to FIG. 9.

DETAILED DESCRIPTION

FIG. 1 shows a schematic diagram of a cutting tool 1 in the region ofthe detail of a punch 2 with a surrounding stripping device 3. Thestripping device 3 is fastened to a fastening plate 5 of the punch via afastening plate 4. The fastening plate 5 for its part is mounted on thecutting tool 1. The fastening plate 5 has a standardized shape. FIG. 1illustrates the situation in which the punch penetrates a metal sheet 6,as workpiece to be machined, in a punching manner. During the punchingprocess, the metal sheet bears against a front surface 7 of thestripping device 3. After penetrating the metal sheet, the punch dipsinto a mating punch 8. The section punched out of the metal sheet fallsthrough a passage opening 9 provided in the mating punch into acollecting container (not illustrated).

As can be clearly gathered from FIG. 1, the stripping device has a frontsurface shape corresponding to the shape of the metal sheet. As aresult, the metal sheet is supported during the punching process and atthe same time is not deformed. The shaping of the front surface of thestripping device can be undertaken on-site at the particular user. As afunction of the forces which occur, the stripping device may be designeddifferently in each case, as illustrated in detail in the followingfigures. FIGS. 2 to 4 indicate an embodiment which is suitable more forsmaller forces, FIGS. 5 to 8 an embodiment which is suitable for greaterforces, and the embodiment according to FIGS. 9 to 11 a variant which issuitable for high forces. The front surfaces of the stripping devicescan be formed such that they differ correspondingly.

FIG. 2 illustrates a longitudinal sectional view of a first embodimentof the stripping device 3. The stripping device 3 is fastened to thefastening plate 5 of the cutting tool via the fastening plate 4, as canbe gathered better in particular from FIG. 3. In this embodiment, thisis undertaken merely by an indicated screw 10, which can be seen betterin FIG. 4. The fastening plate 4 fastens a guide sleeve 11 of thestripping device. As can be gathered from FIGS. 2 and 3, the fasteningplate 4 protrudes inward in its upper region and, in the process,engages over a downwardly protruding section 12 of the guide sleevefitted into the fastening plate. As can be gathered in particular fromFIG. 4, the protruding section 12 is provided only along a subregion ofthe circumference of the guide sleeve. This suffices in order to firmlyhold the guide sleeve and to secure it against tilting. In the region inwhich the screw 10 is plugged through the fastening plate, the guidesleeve is formed without a protruding section, in the same manner as inthe region offset 90° with respect thereto, which can be seen on theleft in FIG. 4. This enables the guide sleeve to be offset by 90° withinthe fastening plate. An elongated hole 14 which is provided in an upperend plate 13 of the guide sleeve and which may alternatively be apolygonal hole can likewise be offset as a result by 90°, which provesadvantageous in certain applications, since fewer different strippingdevices have to be provided as a result.

The guide sleeve 11 is essentially cylindrical and is provided in itsupper region with the end plate 13, which runs essentially at rightangles to the circumferential surface of the guide sleeve and haselongated hole 14. A stripping element 15 is arranged within the guidesleeve and the elongated hole. The stripping element 15 is guided withinthe guide sleeve and is slidable. This is made possible by provision ofa lubricant 16, in particular a solid lubricant. The stripping elementhas a straight section 17 and a protruding section 18. The lubricant 16is provided in the region of the straight section 17. The protrudingsection 18 protrudes essentially as far as the inner surface 19 of theguide sleeve and is guided on this guide surface in a sliding manner. Ascan be gathered in particular from FIG. 3, the protruding section 18 isnot provided over the entire circumference of the stripping element 15,but merely along the longitudinal sides. The straight section thereforehas a different wall thickness, as can be gathered from FIGS. 2 and 3.

The elongated hole and the stripping element have an irregular crosssection. This is distinguished by three straight sides 141, 142, 143 andone curved side 144. Corner transitions 145, 146, which are in each caseprovided with radii, are formed between the two long straight sides 141,142 and short straight side 143. Owing to this irregular and at leastpartially asymmetrical configuration of the cross sections, when thestripping element is installed, the correct orientation thereof can beensured, with rapid and easy installation. In addition, straight,comparatively large surfaces on the stripping element are advantageouslyprovided for absorbing forces when a means of securing against rotationis produced.

In order to provide damping and a restoring mechanism, a spring-elasticelement 21, for example in the form of a rubber spring, is providedbearing against the protruding section 18, on the lower side 20 thereof.Said element, in the same manner as the stripping element 15, surroundsthe punch. However, in contrast to the stripping element, said elementis arranged around the punch concentrically with essentially the samewall thickness. A retaining disk 22, the outer surface 23 of which isessentially aligned with the outer surface 24 of the fastening plate 4,is arranged on the other side of the spring-elastic element. Thisproduces a defined mating surface for supporting the spring-elasticelement.

On the fastening plate 4, a region 50 protruding at the edge over theactual outer surface 24 and a further section 51 protruding in a claw-or clamp-shaped manner are provided. This can best be seen in FIG. 4.The protruding region 50 and the protruding section 51 engage around theouter edge 52 of the fastening plate 5 of the cutting tool. As a result,a centering of the fastening plate 4 and therefore of the entirestripping device 3 and a secure locking to the fastening plate 5 of thecutting tool by means of just one screw 10 are possible.

In the region of the elongated hole 14 in the end plate 13, thestripping element 15 is guided from the outside and, along its passageopening 25, is guided from the inside on the punch which is to beplugged here through said opening. For this purpose, the fit on thepunch is preferably designed as a snug fit.

The front surface of the stripping element 15 is beveled or shaped inaccordance with the shape of the workpiece. The passage opening 25,which is already provided in the stripping element and is intended forpassing the punch through, is also completely driven through thestripping element, as is already indicated by the broken lines in FIGS.2 and 3. In this embodiment, a bevel angle α of up to 5° is preferablyselected. For larger bevel angles, one of the embodiments according toFIGS. 5 to 8 is preferably selected. In these, the bevel angle α ispreferably up to 10°. The further shaping of the front surface of thestripping element 15 is preferably matched to the shaping of theworkpiece to be machined, in particular metal sheet of complex shape. Itis also possible, by means of this matching, to avoid inadvertentmarkings caused by the stripping element on the surface of the punchedworkpiece. Such markings, in particular circular markings, regularlyoccur in the case of the devices of the prior art and lead to a reducedquality of the punched workpieces or to wastage.

In contrast to the embodiment according to FIGS. 2 to 4, in theembodiments according to FIGS. 5 to 8 the fastening plate is formedintegrally with the guide sleeve. In addition, this guide sleeve 26 isdesigned such that it is longer in the region of its straight section 27than the guide sleeve 11 according to FIGS. 2 and 3. The fastening platepart 28 of the guide sleeve 26 has a greater material thickness than thefastening plate 4 according to FIGS. 2 and 3. In addition, as can begathered from FIGS. 6 and 8, two fastening screws 10 and two fixing pins53 can be provided in it to fasten it to the cutting tool or to thefastening plate of the punch. The thicker fastening plate part resultsin greater stability, as a result of which the larger lateral andshearing forces can be compensated for.

In contrast to the embodiments according to FIGS. 2 to 4, the guidesleeve is designed to be of such a length that it can be attacheddirectly on the cutting tool and, in the process, at the same timecovers the fastening plate 5 of the punch having, in particular, astandardized shaping. This can be gathered in particular from FIGS. 5and 7. The covering is merely on one side, as can be gathered from FIG.5, in a manner similar to in the above region 50 according to FIGS. 2 to4, for which reason the circumference of the guide sleeve is not ofuniform length. In the region of the fastening plate of the punch, theguide sleeve is designed such that it is shorter in order to end abovesaid plate.

The difference of the embodiments according to FIGS. 5 to 7 and 8resides in the fact that, although in both cases an elongated hole orpolygonal hole is provided, this is arranged offset by 90°. Thispossibility has already been discussed with reference to FIGS. 2 to 4.The rotation of stripping element or guide sleeve through 90° is clearfrom FIGS. 6 and 8. The remaining design of the stripping element and ofthe guide sleeve and of the spring-elastic element and of the retainingdisk is essentially identical in both embodiments. In all of theembodiments illustrated, after installation and fastening inadvertentrotation is no longer possible, since the provision of the elongatedhole 31 with three straight sides 311, 312, 313 and one curved side 314and with corner transitions 315, 316, which are provided with radii orof a different hole shaped as desired and the corresponding design ofthe stripping element result in the provision of a means of securingagainst rotation which lies in the range of a hundredth of a millimeter.The stripping element preferably consists of high-quality bronze. Theguide sleeve preferably consists of steel. On account of this pairing ofmaterial, a particularly high-quality guidance of the stripping elementin the steel body of the guide sleeve can be produced, with it beingpossible to provide long-term durability or service life of thestripping element. This amounts to approximately five to ten times thestripping devices known hitherto. The only wearing part is thespring-elastic element. However, this withstands more than one millionstrokes and is therefore much more durable than the known strippingdevices.

The protruding section 18 of the stripping element, which corresponds tothe stripping element according to FIGS. 2 to 4 except for thedimensions, may, in addition to the means for securing against rotation,also produce a stroke limit. This takes place by the fact that saidelement can be displaced until at maximum shortly before the end plate13 or 29. By the provision of the means of securing against rotation inthe form of the elongated hole 14, 31 and the corresponding design ofthe stripping element, in addition to the guidance function shearingforces may also be intercepted. Depending on the application, it is alsopossible to undertake a matching to different stem diameters of thepunch by differently sized passage openings 25 or 30 of the strippingelement or of the passage opening 32 of the spring-elastic element.Larger lateral forces which occur can also be intercepted by the largerguide length of the guide sleeve. As in FIGS. 2 to 4, the guidance inrespect of the stripping element again takes place from the inside andoutside, i.e. in the end plate 29 of the guide sleeve 26 and on thepunch along the passage opening 32 of the stripping element 15. In spiteof the partially very different shaping of the front surface of thestripping element, torques acting on the stripping device can beoptimally intercepted by the provision of the guide surface pairings andthe device for securing against rotation.

FIGS. 9 to 11 illustrate an embodiment which is suitable forparticularly high shearing forces or lateral forces. In this embodiment,guide bushings 33 are provided instead of guide sleeves, the guidebushings 33 being arranged within a stripping element 34. The guidebushing 33 runs along the punch (not illustrated). For this purpose, ithas an inner passage opening 35. The stripping element 34 is designed tobe larger than in FIGS. 2 to 8. It is in the form of a truncatedtrapezoid, with large passage openings 39 in which fastening means forfastening the stripping device to the cutting tool fit. This region ofthe stripping element is the fastening section which, instead of aseparate fastening plate and a fastening section as in FIGS. 5 to 8, isformed on the stripping element itself. In order to be able to betterabsorb lateral or shearing forces, fastening to the cutting tool isprovided via two fitting shoulder screws 36. The latter fit in guidebushings 37, 38 which are fitted into steps in the passage openings 39.

As can be gathered from FIG. 11, the fitting shoulder screws 36 arefastened directly in the cutting tool, surrounding the fastening plate 5for the punch on both sides. This corresponds to the constructionaccording to FIGS. 5 to 8. In comparison to the embodiments according toFIGS. 2 to 4 and 5 to 8, the guide length of the stripping element isincreased once again, this length being determined by the shaping of thestripping element and the manner of fastening via three guide bushings.In this case, guidance of the stripping element from the outside andfrom the inside is provided, as can be gathered in particular from FIG.9, along the punch and on the fitting shoulder screws. This embodimentis secured against inadvertent rotation by provision of a specialformation of the region of the stripping element which surrounds the twofitting shoulder screws 36 and is intended for engaging around thefastening plate 5, and by the fastening to the cutting tool via the twofitting shoulder screws (see in particular FIG. 11).

In addition to the embodiments described above and illustrated in thefigures, numerous further embodiments may also be formed, in which ineach case a stripping element which comes into contact with theworkpiece and surrounds a cutting element, at least one guide deviceguiding the stripping element and a means for securing against rotationare provided on the stripping element. A spring-elastic element which islikewise provided is arranged outside the workpiece contact region andserves merely for damping and restoring the stripping device.

LIST OF REFERENCE NUMBERS

-   1 Cutting tool-   2 Punch-   3 Stripping device-   4 Fastening plate-   5 Fastening plate-   6 Metal sheet-   7 Front surface-   8 Mating punch-   9 Passage opening-   10 Screw-   11 Guide sleeve-   12 Protruding section-   13 End plate-   14 Elongated hole-   15 Stripping element-   16 Lubricant-   17 Straight section-   18 Protruding section-   19 Inner surface-   20 Lower side-   21 Spring-elastic element-   22 Retaining disk-   23 Outer surface-   24 Outer surface-   25 Passage opening-   26 Guide sleeve-   27 Straight section-   28 Fastening plate part-   29 End plate-   30 Passage opening-   31 Elongated hole-   32 Passage opening-   33 Guide bushing-   34 Stripping element-   35 Passage opening-   36 Fitting shoulder screw-   37 Guide bushing-   38 Guide bushing-   39 Passage opening-   40 Fastening section-   50 Protruding region-   51 Protruding section-   52 Outer edge-   53 Fixing pin-   141 Long straight side-   142 Long straight side-   143 Short straight side-   144 Curved side-   145 Corner transition-   146 Corner transition-   311 Long straight side-   312 Long straight side-   313 Short straight side-   314 Curved side-   315 Corner transition-   316 Corner transition-   α Bevel angle

1. A stripping device for use with a cutting tool with a cutting elementfor machining a workpiece, the cutting element being movable along alongitudinal axis, the stripping device comprising: at least onefastening piece for fastening the stripping device to the cutting tool;a spring-elastic element which is arranged outside the workpiece contactregion and around the cutting element; a stripping element whichsurrounds the cutting element, wherein the stripping element has anon-circular cross-section and a front surface, the front surface beingdefined by a beveled portion having a bevel angle, the beveled portioncoming into contact with the workpiece along a contact plane, andwherein the contact plane defines a non-zero angle with respect to aplane perpendicular to the longitudinal axis at least when the cuttingelement passes through the workpiece, and wherein the beveled portioncomprises an inner periphery which defines a passage opening throughwhich the cutting element passes, and wherein the bevel angle surroundsthe passage opening and extends from one side of the front surface, overthe passage opening, and to the other side of the front surface; and aguide element having an outer surface with a circular cross-section andhaving an inner surface defining a hole with a non-circularcross-section corresponding in shape with the non-circular cross-sectionof the stripping element, the entire surface of the hole being formed bya single homogenous piece of material, wherein the guide element isconfigured to guide the stripping element and independently prevent thestripping element from rotating.
 2. The stripping device as in claim 1,wherein the stripping element has a cross-sectional shape with norotational symmetry.
 3. The stripping device as in claim 1, wherein thehole has an elongated or polygonal shape.
 4. The stripping device as inclaim 1, wherein the stripping element has a cross-sectional shape withthree straight sides and one curved side.
 5. The stripping device as inclaim 1, wherein the guide element comprises at least one guide sleevearranged outside the stripping element, at least partially surroundingthe stripping element in a guiding manner.
 6. The stripping device as inclaim 1, further comprising at least one guide surface between thestripping element and the guide element, a length of which surface canbe provided as a function of the forces acting on the stripping devicein order to ensure tilt-free guidance.
 7. The stripping device as inclaim 6, wherein the stripping element has an essentially straightsection and a protruding section, and wherein the stripping devicecomprises guide surfaces on the straight and the protruding sections ofthe stripping element.
 8. The stripping device as in claim 1, whereinthe stripping element has at least one guide surface on its insidefacing the cutting element and/or the stripping element and thespring-elastic element are oriented, surrounding the cutting element, insuch a manner that they can be loaded in a manner essentially free fromtorque.
 9. The stripping device as in claim 1, wherein a lubricant isprovided at least in a subregion of the straight section.
 10. Thestripping device as in claim 1, wherein the guide element is formedintegrally with the fastening piece or the guide element and thefastening piece are formed as elements which can be joined together. 11.The stripping device as in claim 1, wherein the spring-elastic elementis arranged between the stripping element or the guide element and thecutting tool and/or within the guide element.
 12. The stripping deviceas in claim 1, wherein at least one protruding region and/or protrudingsection is or are provided on the circumference of the fastening platefor engaging around a fastening device of the cutting tool.
 13. Thestripping device as in claim 1, wherein the stripping element has afront surface corresponding to the workpiece.
 14. The stripping deviceas in claim 1, wherein the spring-elastic element is a rubber spring orconsists of another spring-elastic, restoring or flexible material. 15.The stripping device as in claim 6, wherein the forces are shearing andlateral forces.
 16. The stripping device as in claim 8, wherein the atleast one guide surface faces a stem of the fitted cutting element. 17.The stripping device as in claim 13, wherein the front surface comprisesbronze or another material which can be machined and matched to theshape of the workpiece surface.
 18. The stripping device as in claim 1,wherein the at least one fastening piece is for detachably fastening thestripping device to the cutting tool.
 19. The stripping device as inclaim 1, wherein the beveled portion is planar and defines anon-perpendicular bevel angle with respect to the longitudinal axis. 20.The stripping device as in claim 1, wherein the front surface comprisesa first surface portion at a non-zero angle to a second surface portionwhen the cutting element passes through the workpiece.
 21. The strippingdevice as in claim 1, wherein the defined angle is between 5 and 10degrees.
 22. The stripping device as in claim 1, wherein the frontsurface is shaped in accordance to a shape of the workpiece.
 23. Thestripping device as in claim 1, wherein the entire front surface isbeveled and contacts the workpiece.
 24. The stripping device as in claim1, wherein the defined angle is between 0 and 5 degrees.
 25. Thestripping device as in claim 1, wherein the front surface is formed bybeveling a cylindrical front portion of the stripping element so as toprovide said opening through which the cutting element passes.